Background: The incidence of long-term post-thoracotomy pain is reported to be up to 67%. A relationship between the severity of acute postoperative pain and the development of chronic post-thoracotomy pain has been suggested. Methods: Patients scheduled for elective thoracotomy were interviewed before and one week after surgery to find out if they had pain before surgery and how much pain they experienced postoperatively. The amount of analgesics the patients were given were registered during the first 5 postoperative days. The patients were interviewed by letter 3, 6 and 12 months after surgery to find out if they still had pain due to surgery and to what extent this pain interfered with their daily activities. Results: One hundred and ten patients entered the study. Information about the complete study period was obtained from 67 patients. The incidence of chronic post-thoracotomy pain was 80% at 3 months, 75% at 6 months and 61% one year after surgery. The incidence of severe pain was 3–5%. Chronic post-thoracotomy pain interfered with the patient’s normal daily life in more than half of the patients. High consumption of analgesics during the first postoperative week was associated with a higher risk of chronic post-thoracotomy pain. Conclusion: A significant proportion of patients undergoing thoracotomies will suffer from chronic pain. Surgeons and anaesthetists should be aware of this fact and they should look for effective means of preventing and treating this pain syndrome.